[en] The Fast Mixed Spectrum Reactor is a highly promising concept for a fast reactor with improved features of proliferation resistance, and excellent utilization of uranium resources. In technology, it can be considered to be a branch of fast breeder development, though its operation and implications are different from those of FBR'S in important respects. Successful development programs are required in several areas to bring FMSR to reality, but the payoff from a successful program can be high

[en] Reactor physics and fuel cycle studies, coordinated with heat transfer and material science and structural analysis work has indicated the feasibility potential of the coupled Fast-Mixed Spectrum Reactor (FMSR) concept. This concept employs what are considered reasonable extrapolations of present fast breeder reactor technology to achieve a once-through-and-store reactor fuel cycle. Since the fuel cycle for this reactor is intended to use only natural or depleted uranium for its equilibrium feed, the resultant reactor would have excellent anti-proliferation characteristics. It would also extend utilization of natural uranium resources by a factor of about 15 relative to LWR reactors when on its equilibrium fuel cycle; startup requirements would of course reduce this factor

[en] The fission spectrum uncertainty (variance covariance) matrix is needed in many nuclear data applications. Unfortunately, most modern evaluated data files, with the exception of JENDL3.3, do not include information on the fission spectrum uncertainly. In this paper, the fission spectrum relative uncertainty matrix derivation for the Watt fission spectrum is followed by a more general derivation utilizing some characteristics of any fission spectrum. In the second derivation, the Watt spectrum is used only for the calculation of sensitivity coefficients. (authors)

[en] As part of the Initial Feasibility Study of the Fast Mixed Spectrum Reactor, a series of benchmark calculations were made to determine the sensitivity of the physics analysis to differences in methods and data. Argonne National Laboratory (ANL), the Massachusetts Institute of Technology (MIT), and Oak Ridge National Laboratory (ORNL) were invited to participate with Brookhaven National Laboratory in the analysis of a FMSR model prescribed by BNL. Detailed comparisons are made including a comprehensive study on the adequacy of the fission product treatments

[en] The report summarizes the results of an initial four-month feasibility study of the Fast-Mixed Spectrum Reactor (FMSR). Reactor physics, fuel cycle, and thermal-hydraulic analyses were performed on a reference design. These results when coupled to a fuel and materials evaluation performed in cooperation with the Argonne National Laboratory indicate that the FMSR is feasible provided the fuels, cladding, and subassembly ducts can survive a peak fuel burnup of 15 to 20 atom percent heavy metal and peak fluences of 8 x 10²³ (nvt > 0.1 MeV). The results of this short study have also provided a basis for exploring alternative designs requiring significantly lower peak burnup and fluences for their operation

[en] Spent nuclear fuel (SNF) is currently stored in shielded temporary storage facilities near the nuclear power stations where it was generated. Temporary, at-reactor, storage of SNF is threatening the continued utilization of nuclear power in the US, while presenting a potential terrorist target. The US Department of Energy has recently recommended that Yucca Mountain be developed as the first US permanent geologic repository for high-level radioactive waste at a projected cost of 57 B dollars or ∼800 $/kg of nuclear material. The US Advanced Fuel Cycle Initiative (AFCI) Program has been investigating the economic, social, and environmental viability of sub-critical accelerator-driven systems (ADS) and fast-spectrum critical reactors (FR) for transmuting the hazardous long-lived components of SNF. The overarching goal of the program has been to reduce the number and cost of future repositories. However, the times required for the development and deployment of a Generation-IV fast-spectrum transmuter push the benefits of transmutation half a century into the future. The desire to reap a more immediate benefit forces the consideration of transmutation in a readily available technology, i.e., thermal spectrum reactors. Burning plutonium as mixed uranium-plutonium oxide (MOX) in advanced thermal-spectrum light water reactors (ALWRs) partially addresses the proliferation concerns of SNF, but has not been shown to impact significantly the total SNF actinide inventory. This study examines recycling the minor actinides in ALWRs in an inert matrix fuel (IMF). The NFCSim code is used to model the US reactor fleet plus new reactor deployments that meet an exogenous demand for nuclear power. Repository impact is measured by waste mass, instantaneous and integrated heat production, and toxicity. Performance will be compared to the once-through cycle and transmutation in a fast spectrum burner. Transmutation studies such as this one are intended to provide policy makers with options for resolving the issues in long-term nuclear-waste. (authors)

[en] Recent measurements of the ²⁵²Cf prompt fission neutron spectrum have been fitted with four types of theoretical models: (1) a Maxwell spectrum, (2) a Watt spectrum, (3) a super-position of two Watt spectra representing a typical fission fragment pair, and (4) a relativistic generalisation of (3). Instrumental resolution has been accounted for by exploitation of the fact that the Watt spectrum and the free-gas Doppler broadening kernel are mathematically identical. The Maxwell spectrum is inadequate, as expected, but a Watt spectrum with T_W=1.18 MeV and E_W=0.36 MeV fits all data well, except for those above 17 MeV from one set, with a chi-square that indicates no need for a more refined model. The superposition of two Watt spectra and the relativistic generalisation do not improve the fit. (author). 19 refs, 3 figs

No abstract available

[en] As a part of the Fast-Mixed Spectrum Reactor (FMSR) Project, a study was made on the adequacy of the conventional fission product lump models for the analysis of the different FMSR core concepts. A two-lump fission product model consisting of an odd-A fission product lump and an even-A fission product lump with transmutation between the odd- and even-A lumps was developed. This two-lump model is capable of predicting the exact burnup-dependent behavior of the fission products within a few percent over a wide range of spectra and is therefore also applicable to the conventional fast breeder reactor

[en] The fission spectrum can be analytically represented in several different forms, such as a simple Maxwellian, the Watt fission spectrum, or the more modern and physically sound Madland-Nix representation. A quantitative estimate of the uncertainty matrix associated with the fission spectrum is needed in many nuclear data applications. Criticality safety, neutron cross section adjustment and reactor pressure vessel surveillance dosimetry are just a few examples